The terrorist behind the deadly Paris knife attack was a French citizen born in Russia’s Chechnya who was on the police’s radar for radicalism, authorities said Sunday.

Police identified Khamzat Azimov, 20, as the man who shouted “Allahu akbar” – God is greatest – before killing one person and slashing four others in the City of Light’s lively Opera district Saturday night, AFP reported.

He was shot dead by police, who first tried to stop him using a stun gun.

ISIS called the attacker one of its “soldiers.”

French government spokesman Benjamin Griveaux said the assailant has been categorized as “fiche S” since 2016 – meaning officials had flagged him as being a possible threat to national security on a nationwide database of thousands of people suspected of links to radicalism.

Griveaux rejected criticism that the government was not doing enough to stop terrorist attacks in the country saying, “Zero risk does not exist.”

Azimov was born in the largely Muslim Russian republic of Chechnya but grew up in Strasbourg and became French when his mother obtained citizenship in 2010. Authorities were speaking to his parents Sunday and looking into whether he had any accomplices.

The man had no arrests on his records and didn’t know any of his victims, Interior Ministry spokesman Frederic de Lanouvelle told the Associated Press.

A photo verified by officials to Reuters show Azimov clad in black sweatpants with brown hair and a beard, laying bare-chested and bloodied in the street after being shot.

Witnesses of the attack described him as looking crazed.

“I was working in the restaurant and suddenly I heard a woman screaming … he came and attacked her,” said Jonathan, a waiter working nearby who wouldn’t give his last name. “That’s when the panic started, everyone started screaming and trying to reach our restaurant. … The attacker just kept walking around with his knife in his bloodied hands.”

“Police were quickly on the scene, in less than five minutes. They encircled him and he tried to attack them with a knife but they shot him down,” he told reporters.

When police arrived, officials said the man charged at them shouting, “I’m going to kill you, I’m going to kill you!”

The man he killed was a 29-years-old from Luxembourg and those wounded included two men in their 30s, one 26-year-old woman and one 54-year-old woman, who was gravely hurt, according to AFP.

French President Emmanuel Macron expressed his condolences to the victim’s families.

“France has once again paid the price of blood but will not give an inch to the enemies of freedom,” he tweeted.

Since January 2015, 240 people have been killed in terrorist attacks in France, keeping the country on high alert.

The deadliest of the incidents took place in November 2015, when 130 people were killed in a series of coordinated attacks.

This is the first time an assailant of Chechen origin has carried out a terrorist attack in France, the BBC reported.

Jihadist groups, including ISIS, have long operated in Chechnya and are actively recruiting fighters there to send to Syria and elsewhere.

Ramzan Kadyrov, who was nominated for the Chechen presidency by Russian President Vladimir Putin in 2007 has tried to squash ISIS recruitment but human rights activists say his brutal measures actually help radicalization.